Process to produce hydrogen from underground geothermal reservoirs

ABSTRACT

A geothermal reservoir induces gasification and water gas shift reactions to generate hydrogen. The hydrogen or protons are produced to surface by using hydrogen-only or proton-only membranes in production wells. Energy from the reservoir is produced to surface as protons or hydrogen.

TECHNICAL FIELD

The technical field relates to production of hydrogen from underground geothermal systems.

BACKGROUND OF THE INVENTION

Geothermal Energy is ubiquitous within planets like Earth and many technologies are in use which harvest thermal energy by producing hot water or hot gas or both and byproducts to surface.

In some areas hydrogen and carbon oxides are produced in amounts that could be potentially commercial as a byproduct of geothermal production. These gases are constituents of volcanic gas. The mixture of hydrogen and carbon oxides with steam can be considered a natural synthesis gas that can be used as a fuel or as a feedstock for chemical manufacturing.

The water-gas shift reaction occurs at temperatures and pressures in many underground geothermal systems which are accessible by existing drilling and well completion technology.

The water-gas shift reaction can occur at lower temperatures in the presence of carbon oxides, steam, copper, nickle, iron, or other catalytic materials. The hydrogen produced from these systems can be from deep rock sources such as natural hydrides but also from water through the water-gas shift reaction. Production of hydrogen from underground geothermal systems will tend to push the water-gas shift reaction such that more hydrogen is produced from the system.

Molten salt gasification can take place at temperatures and pressures in many underground geothermal systems which are accessible by existing drilling and well completion technology.

The water-gas shift reaction, molten salt gasification, and other water-splitting processes within a closed system create increased hydrogen concentrations and potentially other components e.g. carbon oxides and oxygen, within the fluids contained in the geothermal system.

Free oxygen can become bound through chemical oxidation reactions within the reservoir and sequestered or produced as oxides.

Surface processes such as steam-methane reforming have used hydrogen selective membranes such as palladium alloys or polymer membranes to separate very pure streams of hydrogen from a mixture of hot fluids.

Graphane, platinum, and sulfonated tetrafluoroethylene based fluoropolymer-copolymers (e.g. nafion) are examples of known hydrogen fuel cell proton carriers, otherwise known as proton selective membranes.

SUMMARY

Hydrogen is often found in deep underground geothermal systems. Hydrogen existing in geothermal reservoirs, or liberated from water within geothermal reservoirs by water gas shift, molten salt gasification, or other processes, can be selectively captured and produced to surface using hydrogen filters such as palladium alloy membranes.

There is a large and growing worldwide demand for hydrogen, which can be used as a chemical feedstock, or combusted at surface to produce power or heat or water, or consumed in fuel cell devices for production of power.

Hydrogen can be a substitute for oil and gas in most energy applications, with pure water as the byproduct of hydrogen combustion. Thus, the use of hydrogen is completely carbon and carbon dioxide free and can be considered as a totally clean fuel.

In broad aspects, methods and systems described herein view sufficiently hot underground layers within planets, where water pre-exists or can be introduced, as significant hydrogen sources.

Oxygen liberated within the reservoir can be produced separately for use at surface, or used to create oxides from naturally existing or injected hydrides for creation of energy and/or oxide products, which may be sequestered or produced. Via the water-gas shift reaction, the oxygen is often bound with carbon in the form of carbon oxides. In underground geothermal systems, the oxygen can also be bound in the form of silicon or iron oxides.

If the membrane chosen is proton selective instead of hydrogen selective, then the entire system can be considered a large natural fuel cell which can be used to produce electricity (power) and water at surface. The excess negative charge created within the Earth can be harvested for additional power through insulated wires, or dispersed by naturally occurring electrically conductive fluids and/or supercritical fluids.

Injection and production wells can take any possible configuration, including but not limited to horizontal, vertical, deviated, multi-lateral, J-shaped, corkscrew, or vermicular configurations. One well can be used for all functions, or one or more wells in a reservoir can be used for specialized functionalities. For example, one well can be used as an injector whereas another can be used as a hydrogen or power producer.

Carbon, carbon oxides, carbon hydrides, copper, or other catalysts can be naturally present or injected into the reservoir. Carbon oxide sequestration can occur in these reservoirs. Hydrides and other chemicals can be cracked and/or hydrogenated within these geothermal systems using hydrogen derived from this process. Oxygen scavenging chemicals may be injected and resultant oxides may either be produced to surface or left sequestered in the reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the present application will become apparent from the following detailed description and the appended drawing in which:

FIG. 1A is a simple schematic view of a first embodiment of the present invention;

FIG. 1B is a simple schematic view of a second embodiment of the present invention;

FIG. 1C is a simple schematic view of an exemplary embodiment of the present invention;

FIG. 2 is a simple schematic view of another exemplary embodiment of the present invention; and

FIG. 3 is a simple schematic view of a further exemplary embodiment of the present invention;

DETAILED DESCRIPTION

Throughout the following description, specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well-known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. The following description of examples of the technology is not intended to be exhaustive or to limit the invention to the precise form of any exemplary embodiment. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

Existing geothermal energy processes produce naturally existing volcanic gases and fluids and solids to surface, and also a portion of injected substances such as water. The Earth warms these fluids in the ground through heat transfer from Earth's interior or volcanic heat or exothermic chemical reactions or thermogenic radioactive decay.

Throughout this specification, numerous terms and expressions are used in accordance with their ordinary meanings. Provided below are definitions of some additional terms and expressions that are used in the description that follows.

As used herein, “reservoir” refers to a subsurface formation that includes a porous matrix which contains fluids. The fluids can consists of water, steam (water vapour), gases (e.g. oxygen, hydrogen, carbon oxides, methane, nitrogen, etc).

The term “in situ” refers to the environment of a subsurface reservoir.

Details are provided for the purpose of illustration, and the methods can be practiced without some or all of the features discussed herein. For clarity, technical materials that are known in the fields relevant to the present methods are not discussed in detail.

FIGS. 1A, 1B, and 1C are diagrams exemplifying implementation of the methods and systems described herein for producing hydrogen from a sufficiently hot reservoir. In these methods, hydrogen is liberated from formation water and produced through a hydrogen selective membrane for production to surface.

The column of buoyant hydrogen ensures the continuous concentration gradient from one side of the membrane to the other. The design shown in FIG. 1C can be extended to a loop well where the heat transfer fluid is injected into the well at surface and the fluids are produced to surface using the same well.

FIG. 2 is a diagram exemplifying one implementation where protons are scavenged by a proton selective membrane and passed toward the surface in a graphane or platinum or nafion composite.

FIG. 3 shows an example of hydrogen-separating composite membranes, viewed in cross-section within a wellbore. Other gas components (CO, CO2, H2S) can be rejected by the membrane.

A. Finding or Making a Hot Reservoir

The reservoir may have an ambient natural temperature sufficient for gasification and water-gas shift reactions to take place within the reservoir. Alternatively, the reservoir may be heated by other means, including but not limited to exothermic reactions via injection, electromagnetic radiation, phonon or acoustic stimulation, steam injection, nuclear reactions, electrical resistance, or magma transference.

B. Gasification and Water-Gas Shift

When the reservoir is at sufficient temperature, gasification and water-gas shift reactions occur with consequent generation of hydrogen. Gas components collect within the reservoir.

C. Production of Hydrogen

Hydrogen is produced from the reservoir through hydrogen-only membranes within the production well. In this manner, the hydrogen sulphide, carbon monoxide, carbon dioxide, steam, and other gas components remain in the reservoir. Since hydrogen is removed from the reservoir, this promotes the reactions to generate more hydrogen.

Protons may be produced from the reservoir through proton-only membranes within the production well. In this manner all other matter can remain in the reservoir, while protons are passed up to the surface using a proton transfer medium such as but not limited to graphane composites.

For the hydrogen-only transport membrane to be placed in the production well, metallic membranes, for example constructed from palladium (Pd), vanadium (V), tantalum (Ta) or niobium (Nb), are mechanically robust but with limited ranges of optimal performance with respect to temperature. These membranes work by a solubility-diffusion mechanism, with the hydrogen dissolving in the membrane material and diffusing to the other side where it is released; this mechanism yields hydrogen flux (moles transport rate per unit area) proportional to the square root of the pressure. To illustrate, vanadium and titanium permeability to hydrogen drops at high temperatures and also forms metal oxide layers that prevent efficient hydrogen separation, making them ideal for anoxic lower-temperature settings. Pd-based membranes have the advantage since their hydrogen permeability rises with increasing temperature. However, Pd membranes are poisoned by hydrogen sulphide (H2S) and carbon monoxide (CO) which are often present within Earth. This can be countered by using Pd-Copper alloys. For cost reduction, multi-layer membranes consisting of Pd—Cu alloy and V, Ta, and Nb could be constructed.

Ceramic membranes, stainless steel membranes, inconel membranes are inert to H2S and CO and can be used at very high temperatures.

In some embodiments the hydrogen membrane is configured to be highly selective to hydrogen (especially if the hydrogen gas is to be used for power generation from a fuel cell at surface), highly permeable to hydrogen, capable of withstanding heating up to or exceeding 800 degrees Celcius, able to withstand H2S and CO gas, robust mechanically given the issues of placing the membranes in the well, and/or capable of being manufactured in geometries that can fit in appropriately configured wells such as long horizontal wells. In some embodiments the membranes can also withstand the partial oxidation stage which will consume carbon and other solid buildup on the exterior surface of the composite membrane.

In some embodiments, the hydrogen produced by the systems and methods described herein can be used in fuel cells to generate power, combusted to produce steam which can be used to generate power, or used as a chemical feedstock.

Although the present specification has described particular embodiments and examples of the methods and treatments discussed herein, it will be apparent to persons skilled in the art that modifications can be made to the embodiments without departing from the scope of the appended claims.

Unless the context clearly requires otherwise, throughout the description and the claims:

-   -   “comprise”, “comprising”, and the like are to be construed in an         inclusive sense, as opposed to an exclusive or exhaustive sense;         that is to say, in the sense of “including, but not limited to”.     -   “connected”, “coupled”, or any variant thereof, means any         connection or coupling, either direct or indirect, between two         or more elements; the coupling or connection between the         elements can be physical, logical, or a combination thereof.     -   “herein”, “above”, “below”, and words of similar import, when         used to describe this specification shall refer to this         specification as a whole and not to any particular portions of         this specification.     -   “or”, in reference to a list of two or more items, covers all of         the following interpretations of the word: any of the items in         the list, all of the items in the list, and any combination of         the items in the list.     -   the singular forms “a”, “an” and “the” also include the meaning         of any appropriate plural forms.

Words that indicate directions such as “vertical”, “transverse”, “horizontal”, “upward”, “downward”, “forward”, “backward”, “inward”, “outward”, “vertical”, “transverse”, “left”, “right”, “front”, “back”, “top”, “bottom”, “below”, “above”, “under”, and the like, used in this description and any accompanying claims (where present) depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

Where a component (e.g. a circuit, module, assembly, device, etc.) is referred to herein, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.

Specific examples of methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to contexts other than the exemplary contexts described above. Many alterations, modifications, additions, omissions and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled person, including variations obtained by: replacing features, elements and/or acts with equivalent features, elements and/or acts; mixing and matching of features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments as described herein with features, elements and/or acts of other technology; and/or omitting combining features, elements and/or acts from described embodiments.

The foregoing is considered as illustrative only of the principles of the invention. The scope of the claims should not be limited by the exemplary embodiments set forth in the foregoing, but should be given the broadest interpretation consistent with the specification as a whole. 

1. A method for treating a reservoir to recover hydrogen, comprising: drilling into a sufficiently hot reservoir to facilitate at least one of gasification or water gas shift reactions to occur to the water within the reservoir; and providing a well within the reservoir and at least one hydrogen or proton permeable membrane producing a produced gas or proton flow from the reservoir via the well and at least one hydrogen or proton permeable membrane, the at least one hydrogen or proton permeable membrane adapted to permit passage of hydrogen or protons from the reservoir to the production stream and to filter gas products other than hydrogen or protons from the production stream.
 2. The method of claim 1, wherein oxygen may be scavenged within the reservoir by oxidation reactions.
 3. The method of claim 1 wherein the reservoir at least near the wellbore may be naturally at sufficient temperature or induced to sufficient temperature via exothermic reactions, thermonuclear processes or decay, phonon or acoustic stimulation, hot material injection, electromagnetic radiation, or electrical resistance.
 4. The method of claim 1 wherein at least one hydrogen or proton permeable membrane comprises at least one of; palladium (Pd), vanadium (V), tantalum (Ta), niobium (Nb), platinum (Pt), or graphene or sulfonated tetrafluoroethylene based fluoropolymer-copolymers based materials.
 5. The method of claim 1 wherein at least one hydrogen-permeable membrane comprises palladium and copper alloys or sulfonated tetrafluoroethylene based fluoropolymer-copolymers or a combination of all.
 6. The method of claim 1 wherein at least one hydrogen permeable membrane comprises a ceramic layer and/or permeable or impermeable structural metal or metal alloy layer and/or a polymer membrane.
 7. The method of claim 1 wherein at least a portion of the at least one hydrogen-permeable membrane is positioned in at least a portion of the well that is within or proximate to the reservoir.
 8. The method of claim 1 wherein the at least one hydrogen-permeable membrane is positioned down stream of the production well.
 9. The method of claim 1 wherein a porous material is positioned within, behind, or in front of the at least one hydrogen-permeable membranes within or downstream of the well.
 10. The method of claim 1 wherein a majority of the produced gas stream consists of hydrogen.
 11. A system for hydrogen recovery from a geothermal reservoir, the system comprising: an apparatus for further heating the reservoir if required; a well positioned to produce fluid from the reservoir; and a hydrogen or proton permeable membrane adapted to permit passage of hydrogen from the reservoir to the production stream and to filter products other than hydrogen from the production stream.
 12. The system of claim 11 wherein the apparatus for initiating heating of the reservoir if needed comprises at least one of: injection of chemical for exothermic reactions, an electromagnet, a radiofrequency antenna, or a hot material injector.
 13. The system of claim 11 wherein the produced hydrogen is consumed in a fuel electrochemical cell device or used to hydrogenate chemicals or combusted to generate steam for power generation or to generate steam for thermal transfer applications.
 14. A method for recovering a substance consisting of hydrogen or protons from a subsurface reservoir containing the substance, the method comprising the steps of: providing a production well within the reservoir; providing at least one permeable membrane in the production well, the at least one permeable membrane configured to permit passage of the substance therethrough while preventing passage of other reservoir contents; allowing the substance to enter into the production well; allowing the substance to pass through the at least one permeable membrane; and producing the substance to surface.
 15. The method of claim 14 wherein the step of producing the substance to surface is subsequent to the step of allowing the substance to pass though the at least one permeable membrane.
 16. The method of claim 14 wherein the step of allowing the substance to enter into the production well is subsequent to the step of allowing the substance to pass though the at least one permeable membrane.
 17. The method of claim 14 wherein the substance is hydrogen.
 18. The method of claim 17 wherein the at least one permeable membrane is a hydrogen permeable membrane.
 19. The method of claim 14 wherein the substance is protons.
 20. The method of claim 19 wherein the at least one permeable membrane is a proton permeable membrane.
 21. The method of claim 14 wherein the production well comprises a production wellbore.
 22. The method of claim 21 wherein the step of allowing the substance to enter into the production well comprises allowing the substance to enter into the production wellbore.
 23. The method of claim 22 wherein the production wellbore is cased with the at least one permeable membrane.
 24. The method of claim 14 wherein the at least one permeable membrane is comprised of a material selected from the group consisting of palladium, vanadium, tantalum, niobium, platinum, grapheme, sulfonated tetrafluoroethylene based fluoropolymer-copolymers, and any combination thereof.
 25. The method of claim 14 wherein the at least one permeable membrane is comprised of a material selected from the group consisting of palladium alloys, copper alloys, sulfonated tetrafluoroethylene based fluoropolymer-copolymers, and any combination thereof.
 26. The method of claim 14 wherein the at least one permeable membrane is comprised of a component selected from the group consisting of a ceramic layer, a permeable structural metal, an impermeable structural metal, a metal alloy layer, a polymer membrane, and any combination thereof.
 27. The method of claim 14 wherein a portion of the at least one permeable membrane is positioned in at least a portion of the well that is within or proximate to the reservoir.
 28. The method of claim 14 wherein the at least one permeable membrane is positioned at a uphole portion of the well.
 29. The method of claim 14 further comprising the step of providing a porous material positioned within, behind, or in front of the at least one permeable membrane positioned anywhere within the well or at an uphole portion of the well.
 30. The method of claim 14 further comprising the step of heating the reservoir to a temperature causing the formation of the substance within the reservoir.
 31. The method of claim 30 wherein the step of heating the reservoir comprises a step selected from the group consisting of injection of a chemical causing exothermic reactions, employing an electromagnet, employing a radiofrequency antenna, employing a hot material injector, and any combination thereof.
 32. The method of claim 17 wherein the produced hydrogen is consumed in a fuel electrochemical cell device, used for hydrogenation reactions, combusted to generate steam for power generation or combusted to generate steam for thermal transfer applications. 